son as oft manual

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SonaSoft Manual

User Interface Software for the FS-

3, FS-3DT, and FS-3DL Sonar Systems

F31552 (Revision 2.1.1)

FarSounder, Inc.


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SonaSoft Manual: User Interface Software for the FS-3, FS-3DT, andFS-3DL Sonar Systems: F31552 (Revision 2.1.1)FarSounder, Inc.

Copyright 2006, 2007, 2008, 2009, 2010 FarSounder, Inc.

FarSounder is committed to providing the best quality and performance possible with our products. As part of this policy, all information herein

is subject to change as new and improved versions of our software and hardware are released.

FarSounder, the FarSounder logo, Power Module, Transducer Module, and SonaSoft are trademarks of FarSounder, Inc.

Maptech, the Maptech logo and Maptech ChartKit are trademarks of Maptech, Inc.


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Table of Contents

1. SonaSoft User Interface Computer Requirements ............................................................... 1

Overview ................................................................................................ .................. 1

Minimum Requirements ............................................................................................... 1

2. The User Interface Workspace ..... ...... ...... ..... ...... ..... ..... ...... ..... ...... ..... ...... ...... ..... ...... ..... .. 2

Overview .... ...... ..... ... .................... ................................................. ........................... 2Managing the Sidebar Workspace .................................................................................. 2

Dragging the Sidebar ......... .................... ...................................................... ....... 3

Resizing Sidebar Windows ................................................................................... 3

Swapping Sidebar and Main Workspace Displays ..................................................... 3

Using The Application Buttons ...................................................... ............................... 3

System Menu .................. ................................................................................... 3

System Status ................ ....................................................... ............................. 4

SonaSoft Help ................. ....................................................... ........................ 6

Exit .................................................................................................................. 6

Color Themes ....................................................................... ............................. 6

3. 3D Sonar Display ................................................................... ........................................ 7

Overview ........................ ...................................................... .................................... 7

3D Volumetric/Standard View ...... ..... ...... ........................................................ ............. 8

Profile View .................................................................. ............................................ 8

Forward Looking Alarm Use ................................................................................ ........ 9

Alarm Configuration ............................... ................................................. ........... 9

Alarm Operation .................................................... ........................................... 10

Menu Bar Controls ..................................................................................... .............. 11

Processor Settings ............................................................................................. 11

Standard/3D View ............................................................................................. 11

Activate Alarm ............................................................ ..................................... 11

Color Map to Depth/Signal Level .................................................. ...................... 11

Mouse Controls ....................... ............................................... .................................. 12

Mouse Drag Left Button (Any Direction in 3D View) ............................................. 12

Mouse Drag Right Button (Up and Down) ............................................................ 12Mouse Hover Over Color Scale (When Shown) ...................................................... 12

Mouse Hover Over Color Scale Extent Numbers .................................................... 12

3D Sonar Processing Options ...................................................................................... 12

Processing Mode Drop Down Selector .................................................................. 12

Detect Bottom Check Box ...... ...... .... .................................................................. 13

Auto Squelch Check Box ...... ...... ..... ... .................................................. ............. 13

Bottom and In-water Squelch Controls ..................................................... ............ 13

Control Settings Examples .......................................................................................... 14

4. Chart Display ........ ................................................................ ....................................... 19

Overview .............................. ................................................................................... 19

Menu Bar Controls ........................ .................................................... ....................... 19

Open ............................................................................ .................................. 19

Auto Center ............................. .................................................... .................... 19Zoom In .............................. ............................................................................ 20

Zoom Out ............................ ............................................................................ 20

Show Scale .......................................... ............................................................ 20

Mouse Controls ............................................................................ ............................ 20

Left Button Mouse Drag .................................................................................. .. 20

Right Button Mouse Drag .................................................................... .............. 20

Configuration Manager Options ...... ...... ..... ...... ... ......................................................... 20

History Length ........................................................... ...................................... 21


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Show Heading ........................ ........................................................ .................. 21

Show Lat/Long of Cursor ................................................................................... 21

5. Nav Info Display ............................................................. ............................................. 22

Overview .............. ........................................................ ........................................... 22

Configuration Manager Options ................................................................................... 22

6. Connecting NMEA Devices ..... ...... ..... ...... ...... ..... ...... ..... ..... ...... ..... ...... ..... ...... ...... ..... .... 24

Overview .............. ........................................................ ........................................... 24COM Port Configuration ............................................................................................ 25

COM Port Check Box ............ ........................................................ ................... 25

Baud Rate Drop Down Box ................................................................................ 25

Show Trace Button ................................... ....................................................... . 25

Re-Scan for Available Ports Button ...... ..... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ... 25

NMEA Message Selection .................................................................................. 25

7. System Settings Options ................................................................................................. 27

Overview .............. ........................................................ ........................................... 27

System Depth Units ...................................................... ............................................ 27

System Range Units ................ ....................................................... ........................... 27

Set Vessel Draft ... ........................................................ ............................................ 27

Advanced Settings ................................................. ................................................... 28

A. Understanding Interference and Other Limitations ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 29Overview .............. ........................................................ ........................................... 29

Other Sonar Interference ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ... 29

Bubble Cloud/Wake Interference ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ... 31

Sea State Limitations ................................................................................................. 32

Vessel Speed Limitations ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ..... ...... ..... ...... .. 32

B. Understanding Water Depth Performance .... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ... 33


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List of Figures

2.1. The user interface workspace .......................................................................................... 2

2.2. Left Click and Drag to resize the sidebar workspace ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 3

2.3. The System Menu .............. ........................................................ .................................. 4

2.4. System Status display window ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... .... 5

3.1. The 3D Sonar Display ................................................................................................... 73.2. Standard Mode .................................................. ........................................................ ... 8

3.3. Alarm Volume shown in red ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... . 9

3.4. Alarm configuration settings ..... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... 10

3.5. Alarm acknowledge button ..... ..... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ... 11

3.6. Processor Configuration Window ...... ..... ...... ..... ...... ..... ..... ...... ..... ...... ..... ...... ...... ..... ...... 12

3.7. Bridge piling used in control setting images ......... ..... ..... ...... ..... ...... ..... ...... ...... ..... ...... .... 15

3.8. A sea floor and a single piling target with "good" settings ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 16

3.9. Color mapped to signal strength with "poor" settings ......................................................... 17

3.10. Color mapped to signal strength with "somewhat poor" settings ... ... ... ... ... ... ... ... ... ... ... ... ... .. 18

4.1. SonaSoft Chart Display ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... .. 19

4.2. Chart Display Configuration Manager Options ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 20

5.1. The Nav Info Display .................................................................................................. 22

6.1. COM Port NMEA configuration options ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ...... 24

7.1. System Settings dialog box ........................................................................................... 27

A.1. Echo sounder interference ............................................................................................ 30



A.4. Wake interference ..... ...... ..... ...... ...... ..... ...... ..... ...... ...... ..... ...... ..... ..... ...... ..... ...... ..... ... 32


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Chapter 1. SonaSoft User InterfaceComputer Requirements

OverviewThe SonaSoft software package has significant hardware resource requirements. Performance may be

affected if SonaSoft is run on a platform that does not meet these requirements. It is recommended

that no other software applications are run during SonaSoft operation. As with any shipboard electronic

systems, it is highly recommended that both the user interface computer and the FarSounder Power Module

be powered through a UPS.

Minimum Requirements

Processor Type: Core2 Duo

Processor Speed: 2.6 GHz minimum

Front Side Bus: 800 MHz

Memory size: 1 GB minimum

Memory Speed: 533 MHz Dual Channel

Video Card: Fully OpenGL and CUDA compatible (nVidia works well)

Video Card Memmory Size: 1 GB minimum

Video Card Resolution: 1280 x 1024 minimum

NIC: 1 Gb/s minimum

Operating System: Microsoft Windows XP Pro (US Version)

Serial: RS-232 or NMEA interface port

Optical Drive: CD-ROM required

Keyboard: yes (set up only)

Mouse/Trackball/HID: yes

Recommended video card:

- NVIDIA GeForce 9800 GT


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Chapter 2. The User InterfaceWorkspace

Overview

Figure 2.1. The user interface workspace

The SonaSoft user interface is divided vertically into two main sections called workspaces. On the left

there is the "main workspace", and on the right there is the "sidebar workspace". These workspaces contain

display windows for the different types of information displayed by SonaSoft. The user can move a

view from one workspace to the other at any time. In the main workspace, only one view is visible at a

time. In the sidebar workspace, several windows are visible at a time, but they are much smaller.

The user can interact with the workspace through the following actions:

Managing the Sidebar Workspace

Resizing the Sidebar

Using the Application Buttons

Managing the Sidebar Workspace

Windows in the sidebar workspace have a vertical window resizer bar along their bottom edge. They also

have a left arrow button which when pressed will cause the selected side bar window to swap places with

the main workspace window. Some display windows include a menu bar at the top of the window. Boththe left arrow button and the windows menu bars will only be displayed when the mouse is within a sidebar

window's frame. This way more display realestate is used for displaying pertinante navigation information.

Note that when moved to the main workspace, no arrow buttons are ever displayed and menu bars are

always visible.


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Dragging the Sidebar

Figure 2.2. Left Click and Drag to resize the sidebar workspace

Between the two workspaces there is a vertical bar called the sidebar resize splitter. The user can drag thesplitter with the mouse to resize the sidebar. To hide the sidebar (and all the windows it contains), drag the

resize splitter to the right side of the screen. To quickly toggle between showing and hiding the sidebar

workspave, double click on the resize splitter.

Resizing Sidebar Windows

The sidebar window views always take up the full width of the sidebar. As a result, the only way to resize

the window is the sizer bar along the bottom border. To resize a sidebar window, click on the resizer bar

and drag with the mouse while holding down the left mouse button.

Swapping Sidebar and Main Workspace Displays

The Swap-with-Main-Workspace Button moves a display from the sidebar workspace and places it in

the main workspace. It is located on the dropdown toolbar. The view previously displayed in the main

workspace is moved to the location sidebar where the new display in the main workspace was previously

located.

Using The Application Buttons

At the very top left of SonaSoft, are two buttons. These buttons are used to access menus and options

for advanced controls and features.

System Menu


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The system menu button is shaped like a gear. Clicking this button displays the system menu. This menu

provides access to:

Configuration options for various components

System Status display

Help Documentation

About Panel

Exit button

Information about the particular configuration options available for each component is described in the

individual component help descriptions.

Figure 2.3. The System Menu

System Status

The System Status display window displays real-time status information produced by various components

of SonaSoft. Some components include a status indicator icon. This icon is a circle colored either Green,


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Yellow, or Red. Green indicates all systems are functioning properly. Yellow indicates there is a system

warning. Red indicates there is a serious problem with part of the system.

Figure 2.4. System Status display window

Figure 2.4, System Status display window shows the System Status display with three indicators and a

hydrophone (receiver) waveform display. The first indicator shows that the Sonar Processor is properly

configured and is in the middle of processing a ping.

The second indicator shows that the software is listening for NMEA messages over the serial port. The

status of that component shows that it is listening on COM1 at 9600 baud. If more than one serial port

is enabled, multiple ports would be listed here and the baud at which they are connected. These ports are

configured under the Configuration Manager's NMEA Settings menu.

The third indicator shows that SonaSoft is currently connected to the Sonar and is awaiting data from the

sensor. It also indicates the sonar's current roll and pitch orientation relative to the earth in degrees. This

indicator may display a yellow or red status if there are problem connecting to the Transducer Module.

The Hydrophone Data display is somewhat different. It is a graphical display of hydrophone data. This

display is very useful for debugging purposes and to confirm the presence of echo sounder interference.

In this display, the waveform of a single receiver channel is shown on the left with the start of the echo's

timeseries at the far left. On the right portion of this display is a graphic of the receiver's transducer array.

Each box represents the spatial location of an individual hydrophone. Clicking on one of the boxes, selects

that channel for the waveform display. Note that the four corner channels are always blank.


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SonaSoft Help

The help button icon is a circle with a question mark in the middle. Clicking this button brings up the

SonaSoft documentation.

Exit

The exit button is square with an X-shape through the center. Clicking this button will shut down

SonaSoft.

Color Themes

The color themes button is shaped like three vertical rectangles. Clicking this button opens a simple menu

which lists the available color themes. Each theme is a set of colors that facilitates the use of the software

in various lighting conditions. Currently, the software supports Day, Dusk, Night, and Red color themes.

A theme may be selected by clicking on a theme from the list.


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Chapter 3. 3D Sonar Display

Overview

The 3D Sonar Display is the window where FarSounder's 3D Forward-Looking Sonar information isshown. In this view, the user is given a 3-dimensional picture of the sea floor ahead of the vessel along

with in-water targets. FarSounder's processing algorithms employ spatial classification techniques which

are used to differentiate between the sea floor and in-water targets. The sea floor is displayed as a smooth

continuous surface while in-water targets are displayed as small spheres, also known as voxels, which

represent the target's 3D location. All FarSounder sonars are specified as 8 water depth sonars. This means

that they can map the sea floor out to a distance of at least 8 times the depth of water in which the sonar

is operating. Beyond their water depth capabilities, the products can still detect in-water targets out to the

full range of the system.

The user can select between various display modes such as the 3D volumetric display, which allows the

user to rotate the 3D image with real-time perspective, and the standard display, which shows the 3D

information in a look-down display (much like a radar view, except below the water).

The Sonar View consists of four main components. They are: the 3D volumetric/standard views, the profile

view, the menu bar, and the color scale. These are shown in the figure below. Additionally, the user can

set an alarm, display 2D depth profiles ahead of the vessel at a user selected bearing, and configure other

advanced options in the display. This display also has various options in the Configuration Manager.

Figure 3.1. The 3D Sonar Display


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3D Sonar Display

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3D Volumetric/Standard View

This view shows the data in either 3D Volumetric or Standard modes. To switch between these modes,

click the mode button in the menu bar.

In the 3D volumetric mode (as shown above), the data is shown with shading and perspective on. Color is

mapped to depth, where blue is deep and red is shallow as defined in the color scale. Any mouse movement

while clicking and holding the left mouse button will rotate the 3D entire volume of data. Any mouse

movement while clicking and holding the right mouse button will zoom the data in and out.

Figure 3.2. Standard Mode

In standard mode, the data is shown with perspective turned off (orthographic projection) with the user

looking down on the data. This looks much like a common radar display. However, where radar gives a

picture of what is above the water, FarSounders sonar displays a picture of what is below the water. As

with the 3D volumetric mode, the standard mode has color mapped to depth and zoom capabilities.

In both modes, a white line (or plane) is shown. This is the Profile Selector. The Profile Selector denotes

the angle along which a 2D depth profile ahead of the vessel is shown in the Profile View. The number

at the end of the profile selector denotes the bearing of the profile selector relative to the vessel's bow or

the actual compass heading. This option is configured in the 3D sonar view's configuration options. The

depth profile slice specified with the Profile Selector is shown in the Profile View.

Profile View

The Profile View shows the depth profile (bathymetry) ahead of the vessel at the bearing selected by the

Profile Selector in either the 3D Volumetric or Standard View. The bearing angle of the Profile Selector

and the depth profile currently selected is shown in the lower left corner of the Profile View. In the Con-

figuration Manager options, the user can select between displaying the Profile Selector bearing relative to

either the vessel or the absolute heading.


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3D Sonar Display

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Forward Looking Alarm Use

The user can define an alarm which will automatically notify the user of potentially hazardous obstacles.

The user can define the area of surveillance for the alarm by depth, minimum range, maximum range, and

field-of-view angle width. The user is notified by both visual and audible notifications. Additionally, the

user can specify the number of hits before the alarm is triggered.

Figure 3.3. Alarm Volume shown in red

Alarm Configuration

The user definable alarm is configured under the System Menu's 3D Sonar Display option. When config-

uring the alarm, the user can define the volume of water within which targets will trigger the alarm. The

trigger area is defined to be the volume of water bounded by 4 thresholds: Max Depth, Min Range, Max

Range and Field-of-View (FOV) angle.


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3D Sonar Display

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Figure 3.4. Alarm configuration settings

The FOV setting specifies the sector width of the alarm trigger volume in degrees. For example 40 means

that only targets within 20 to either side of the bow will be able to trigger the alarm. The Max Depth

setting specifies the maximum depth of the alarm trigger volume. The Min Range setting specifies the

minimum range extent of the alarm trigger volume. The Max Range setting specifies the maximum range

extent of the alarm trigger volume. The Max Depth, Min Range, and Max Range settings are displayed

using the unit of measure defined in the Configuration Manager's System Settings.

Like any marine sensor (radar, echo sounder, etc) the FarSounder sonar systems may detect spuriousnoises. These noises include reflections from bubbles in the water column and small bits of debris in

the water. The alarm hit number specifies the number of pings in a row that a target must be detected

within the alarm volume to trigger the alarm. By specifying a number higher than 1 for the hit number,

false alarms can be reduced. For every ping with a detection within the alarm volume an internal counter

is incremented. For every ping without a detection within the volume the internal counter is decremented

until reaching a minimum value of 0. If the counter value reaches the hit number specified by the user,

the alarm is triggered.

The last configuration option is check box called Blink Screen On Alarm. When checked, the 3D Sonar

Display screen will blink if the alarm is triggered. If not, the display will not blink. This setting does not

affect the audible alarm notification.

Alarm Operation

Once configured, the alarm is simple to use. The alarm can be turned on by clicking the Alarm button in

the Menu Bar at the top of the 3D Sonar Display window. Once active, the alarm conditions will take effect.

The alarm will ONLY be triggered if the button is set to active. When active, the alarm button is depressed.


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Figure 3.5. Alarm acknowledge button

Should the alarm be triggered, a warning will sound, the 3D Sonar Display window will blink blue, and

an alarm acknowledge message box will appear in the lower left corner of the sonar viewer window.

Simply click the acknowledge alarm message box to acknowledge and temporarily silence the alarm. For

example, the vessel may be passing by a shallow area which triggers the alarm. After the user acknowledges

the alarm, it will not sound again even if alarm conditions are met until the alarm acknowledge time has

passed. If alarm conditions still exist after the alarm acknowledge time has passed, the alarm will sound

again.

Menu Bar Controls

Processor Settings

Click this button to toggle display of the Processor Settings toolbar (see section entitled "3D Sonar Pro-

cessing Options).

Standard/3D View

Click this button to toggle between standard view mode and 3D view mode. By default, both of these

modes map the color of sonar targets to depth, where blue is deep and red is shallow. The user can define

these values with the Color Bar. Additionally, for advanced applications, the color map can be changed

so that color indicates the strength of the received signals from a particular target. In this mode, red is

loud and blue is quiet.

Activate Alarm

When depressed, the alarm is active, and will be triggered by objects in the alarm volume.

Color Map to Depth/Signal Level

Toggles between color mapped to Signal Level in decibels and color mapped to depth. The color scale

will be changed to the user's last color extent values for the color map currently being shown.

The user can change the scale's extents by clicking on the red or blue extent values. A number pad will

then pop up allowing for mouse or keyboard specification of a new value. The new settings will be active

on the next ping.

Note that with color mapped to Depth, the depth indicated is either "Depth Below Surface" or "Depth

Below Keel" as noted by a lable in the bottom left corner of the 3D sonar display. With color mapped to

Signal Level, the numbers correspond to the same scale as the Squelch settings as described in "3D Sonar

Processing Options".


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Mouse Controls

Mouse Drag Left Button (Any Direction in 3D View)

Left dragging has two different behaviors, depending on where the user starts dragging the mouse.

When positioned at the end of the profile selector, a large double sided arrow will appear. In this case, left

dragging will change the angle of the profile selector.

When in 3D mode and not over the end of the profile selector, left click dragging the mouse will rotate

the 3D display volume.

Mouse Drag Right Button (Up and Down)

In the 3D view, this action will zoom in and out, enlarging the data (up) and shrinking the data (down).

This control is valid in both 3D Mode and Standard Mode.

In the Profile View, this action changes the aspect ratio of the profile view.Note: The angular line extend-

ing downwards from the boat icon represents a 45 degree angle from horizontal.

Mouse Hover Over Color Scale (When Shown)

This action shows the depth or decibel value for a given color on the color scale.

Mouse Hover Over Color Scale Extent Numbers

This action shows an edit box that can be used to enter new color scale extent values. Newly changed

values will be active on the next ping.

3D Sonar Processing OptionsLike other marine electronics sensors, there are processing control settings for the FarSounder sonars.

FarSounder has developed autonomous processing algorithms that intelligently control various stages of

the processing routines, and automatically remove most of the noise in the image without user interac-

tion. The few controls that require user interaction are found in the Processor Settings tool bar (Figure 3.6,

Processor Configuration Window). This tool baris displayed when the user clicks on the "Processor

Settings" button at the top of the 3D Sonar Display (see Figure 3.1, The 3D Sonar Display). Working

from left to right, this window has the following controls: Processing Mode Drop Down Selector, Detect

Bottom Check Box, Auto Squelch Check Box, Bottom Squelch Slider, and In-Water Squelch slider.

Figure 3.6. Processor Configuration Window

Processing Mode Drop Down Selector

The processing mode selection drop down sets the system's range and field of view while pinging.Note:

At least one ping must be processed before this value can be changed.


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3D Sonar Display

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90 x 110m (360 ft) (FS-3, FS-3DT, FS-3DL)

90 x 220m (720 ft) (FS-3, FS-3DT)

90 x 330m (1080 ft) (FS-3, FS-3DT)

60 x 440m (1440 ft) (FS-3DT only)

Alternating between 90 x 330m (1080 ft) and 60 x 440m (1440 ft) (FS-3DT only)

Detect Bottom Check Box

If this check box is checked, then the processor will attempt to detect the bottom so that it may be drawn as

a surface in the 3D Sonar Display. If this check box is not checked, then there will be no surface drawn in

the 3D Sonar View. This feature is useful when operating in water depths beyond 160 feet (approximately

50 meters) deep. If Detect Bottom is checked in deep water conditions, the processing software may

falsely interpret in-water targets as the bottom and create some strange images.Note: If this check box is

not checked and there is a bottom, then that bottom may show up as a large number of targets, provided

the in-water squelch is set to a low enough value.

Auto Squelch Check Box

If this check box is checked, then the processor will attempt to detect the bottom automatically, without

considering the user's Bottom Squelch setting (see "Bottom and In-water Squelch Controls"). Most of the

time, the Auto Squelch mode will perform better than manually setting the Bottom Squelch level. This

setting has no effect on In-Water Targets.

Bottom and In-water Squelch Controls

The 3D sonar processing technology that FarSounder has developed and integrated into the sonar systems

utilizes spatial classification and correlation techniques to identify particular targets as either part of the

sea floor/river bed or as an in-water target. The classification of targets into distinct target categories is animportant part of FarSounder's signal processing and image display chain. Different target categories are

processed differently utilizing a priori information pertaining to the target category type. For example, the

sea floor is generally comprised of many small reflectors as part of one larger continuous surface, while

in-water targets are typically comprised of fewer target points and often have many angles and surfaces

which face the sonar. By exploiting these and other differences, FarSounder's products are able to operate

effectively in shallow water and at navigationally significant ranges.

To produce the most complete pictures, some parameters of the processing controls may need to be modi-

fied to suit the environment. These parameters are controlled by the Bottom Squelch and In-water Squelch

sliders. These controls can fine-tune the processing system in the event that too few targets are displayed,

or too many targets are making the view difficult to understand.

To effectively use the Bottom Squelch and In-water Squelch it is important to understand how differentsonar targets reflect sound waves. The reflections from different targets are detected by the system as

a signal with some energy level relative to the energy level of the ambient noise in the water and the

electronics. This relationship between the signal level and the noise level is called the Signal to Noise

Ratio (SNR). The larger the SNR, the better the system will detect a target and separate it from the noise.

SNR is generally controlled by two metrics: the acoustic reflectivity of a target and the range of the target.

Targets that are physically larger, have a large gas content, have large surfaces facing the sonar, or are

very hard will generally be more reflective than targets that are physically small, have high water contents,

have surfaces not facing the sonar, or are very soft; the higher the reflectivity of the target, the higher the


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SNR from the reflected signal. Additionally, a target at close range will have a higher SNR than the same

target at far range.

Because of these two controlling metrics, the system must filter out targets that have low signal levels at

varying ranges. These signals may be from targets that are too far away or physically too small to detect.

Larger, more reflective targets will be detected at longer ranges than smaller, less reflective targets.

Note that when changing any of the processor settings (ie. Squelch levels, processing ranges, etc.) changes

will not take effect until the next complete processing cycle.This typically means 2 pings after adjusting

the control, you will see the change, since generally when you see an image that needs adjusting there is

already another ping processing with those same settings internal to the software. Changes will be applied

to the next "fresh" ping.

Bottom Squelch Control Slider

As described previously, the SNR for a particular target decreases as the range of the target increases.

This means that very small targets at close range may have the same SNR levels as large targets at long

range. Therefore, in order to keep very small (less reflective) targets at very close ranges from cluttering

the display, potential targets must also be filtered based on their reflectivity. This equates to filtering the

signal levels after they have been normalized based on their range.

The Bottom Squelch Slider controls the target size (reflectivity) cutoff. This level is used to filter out

targets that are very small and have low reflectivity. The level set by this control specifies how large a

target's range-normalized signal must be before it is accepted as a possible target (rather than just noise

from debris and small bubbles).

In general, when this control is set to a lower level, the bottom will become fuller. However, the cost of

this is some smaller in-water targets may be caught as part of the bottom. A value of 145-155 is typical

for most conditions.

When making Bottom Squelch adjustments, typically a change of a few dB is all that is needed. Remember

that changes generally take 2 pings to become visable.

In-Water Squelch Control Slider

Variations in target characteristics also have effects on how noise is related to in-water targets. Generally,

in-water targets are louder (more reflective) targets than the sea floor, and require a different target size

(reflectivity) cutoff. The In-Water Squelch slider controls the target size cutoff for in-water targets. The

value of this slider control operates independantly from the Bottom Squelch control. In general, setting

this control to a lower level will detect smaller, less reflective in-water targets.

For best operation, the user should typically set the Bottom Squelch control at a place where the bottom is

detected well, and then adjust the In-Water Squelch until clutter from in-water debris is filtered effectively.

A value of 165-175 is typical for most conditions. Like with radar, it is recommended that the squelch be

set so that occasional false alarms are detected. This will help to ensure that real targets are not missed

due to squelch levels set too high.

When making In-Water Squelch adjustments, typically a change of a few dB is all that is needed. Remem-

ber that changes generally take 2 pings to become visable.

Control Settings Examples

Often there is a disconnect between reading about control settings and actually using them. The following

discussion will use an example ping of a bridge piling in deep water in an effort to illustrate the aforemen-


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3D Sonar Display

15

tioned controls. For this discussion, a single ping of a deep water bridge piling (Figure 3.7, Bridge piling

used in control setting images) is processed with various control settings. This environment was used

because of the simple sea floor and simple in-water target environment. When learning to use the sonar,

it may be useful to practice adjusting the settings in a simple environment where you have a good idea

of what is actually under the water. Like any navigation tool, you should practice using the tool and get

comfortable with the display and data representation in good weather and in good conditions so that when

you find yourself in situations where you really need the sonar, you will be comfortable and well versedin its operation. Note that once the sonar's settings are set appropriately, it will generally not be necessary

to frequently change the settings unless the water environment changes drastically.

Figure 3.7. Bridge piling used in control setting images

Figure 3.8, A sea floor and a single piling target with "good" settings shows a 3-dimensional image

generated from a single ping of a deep water bridge piling. The piling is clearly detected ahead of the

vessel at about 165 meters (545 feet) range. In this image, color is mapped to depth, and appropriate control

settings have been used. The control settings used to generate this image are shown at the top of the screenshot. In this image, Automatic Bottom Squelch is used by selecting "Auto Squlech" and In-Water Squelch

is set to 183 dB. Let us now discuss how it was determined that these are good settings.


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3D Sonar Display

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Figure 3.8. A sea floor and a single piling target with "good" settings

Hint: When adjusting the Processor Control Settings, try imaging a simple environment.

Begin by setting the controls to values within their suggested range. Try using "Auto Squelch" rather than

manually setting the Bottom Squelch and In-Water Squelch: 175 dB. When setting these values it is im-

portant to try and find good settings for the sea floorbefore concentrating on displaying in-water targets.

Generally the "Auto Squelch" setting for Bottom Detection will perform better than manual settings. How-

ever, if you do want to use manual Bottom Squelch settings try around 150 dB. When operating manually,

if you are unhappy with the sea floor image, try lowing the Bottom Squelch value just a little. Remember

that the sonar is an 8 water depth sonar. This means that the sea floor can be mapped out to 8 times the

depth of water below the transducer. Sometimes you may find slightly less coverage at the edge. Often,

you will find much better that 8 water depth performance. The lower the Bottom Squelch, the more erratic

the sea floor becomes. Generally you do not want or need to change this setting. If it is set too low, noise

in the raw sonar data may be mistaken as the sea floor. This noise comes from electrical noise spikes and

acoustic reflection from small bits of debris or bubbles in the water column. These noise levels should befiltered out with the proper setting of this control. Some signs that this value is set too low may include:

1. Random humps in the sea floor that are not present for more than one ping. These may cause drastic

irregularities in the bottom contours.

2. Extremely long range bottoms that end up going very deep at the longest ranges.

Note that in very soft, silty bottom environments, the bottom may not be detected well or at extended

water depths. Even in this case though, in-water targets will be well detected. Large rocks, pilings or other


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3D Sonar Display

17

hard targets sitting in the silt will also be detected well. These targets may be shown as in-water targets

rather than the sea floor.

Generally, if the Bottom Squelch is set too low, there will be bottom spikes indicating very shallow water

at or near the surface and at VERY close range. Additionally, if the bottom has narrow but tall lumps,

this is also a sign that the Bottom Squelch is set too low. You may find that there is a range of values for

the Bottom Squelch setting that look good and have very little effect on the bottom. Again, in most cases,

using "Auto Squelch" for the Bottom Detection will work better than the manual settings.

Figure 3.9, Color mapped to signal strength with "poor" settings shows the same ping with poor pro-

cessor settings. In this image, color has been mapped to signal strength. Red shows that a target is highly

reflective, where blue shows that a target is less reflective. One can clearly see that there is a nice regular

looking sea floor, but there is a lot of in-water target clutter. In this test case, we know that there should be

a single in-water target that is a strong reflector; the piling. In the figure, one can clearly see that there is a

single very reflective in-water target (the red blip). Its position corresponds precisely to where the piling

was visually sighted. All of the other in-water targets are most likely noise blips caused by poor settings.

Certainly, there may be other legitimate in-water targets that are in the water column and not visible to

the eye above the water. However, they would likely be much louder than the sea floor, and nearer to the

signal level of the piling.

After finding settings for the sea floor, the In-Water Squelch should be adjusted in order to remove falsein-water targets and clutter. As mentioned previously, in-water targets are typically much more reflective

than the sea floor. Because of this a separate, higher level cutoff is needed for in-water targets to avoid

showing clutter and detecting false targets.

Figure 3.9. Color mapped to signal strength with "poor" settings


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3D Sonar Display

18

Noise blips are spurious and are not generally consistent from ping to ping. If an in-water target is detected

on multiple pings, even if it is of a lower signal strength, it is probably a legitimate target. Before changing

the settings too much, look at multiple pings for consistent, low signal strength targets. From this single

image, it is clear that the in-water target cutoff needs to be increased.

Hint: Map color to signal strength in order to identify a single target against noise blips

In Figure 3.10, Color mapped to signal strength with "somewhat poor" settings, the Bottom Squelch

is still set to "Auto Squelch" and the In-Water Squelch has been increased. There are less in-water blips

than in Figure 3.10, Color mapped to signal strength with "somewhat poor" settings, but still there is

much more than just the single piling shown. It is likely that the In-Water Squelch is still too low. Notice

that many of the in-water targets are very close in signal strength to the sea floor, and that they appear to

be truncated by the surface of the sea floor itself. These two characteristics are indications of noise blips

rather than less reflective, legitimate targets. The original image generated in Figure 3.8, A sea floor and

a single piling target with "good" settings utilized a slightly higher In-Water level setting. This slight

increase was enough to raise the in-water target cutoff slightly and clean up the image. During the rest of

the cruise, these settings did not need to change.

Figure 3.10. Color mapped to signal strength with "somewhat poor" settings


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19

Chapter 4. Chart Display

Overview

FarSounder's Chart Display provides SonaSoft with basic chart plotting capabilities. The Chart Displaysupports any BSB standard digital chart. BSB charts can be downloaded free from NOAA for all U.S.

waters. Charts for other waters can be downloaded from other agencies. For convenience, many companies

sell BSB chart and photographic image collections for most of the world's waters which can be loaded

by the Chart Display. The Chart Display window provides various chart plotting functionalities, such as

showing the position of the vessel on the chart, zooming in an out on the chart, generating a dynamic

range scale, measuring distance between two points on the chart, showing vessel heading, and showing

Lat/Long coordinates of the cursor position. Figure 4.1, SonaSoft Chart Display shows a screen shot

of SonaSoft's chart display. The various features and controls are explained below.

Figure 4.1. SonaSoft Chart Display

Menu Bar Controls

Open

The Open button will display an open file dialog from which the user can select chart file to open. The last

chart opened will automatically be loaded the next time SonaSoft is restarted.

Auto Center

When depressed, the map and the vessel graphic will be centered in the window with any new GPS infor-

mation received by the Digital Chart Viewer. Otherwise, the vessel will move across the map with each

latitude/longitude position update.


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Chart Display

20

Zoom In

Clicking this button will zoom in on the scale of the chart. If auto center is depressed, then the boat will be

at the center of the newly zoomed view. If auto center is not checked, then the zooming will be centered

on the position of the cursor.

Zoom OutClicking this button will zoom out on the scale of the chart. If auto center is depressed, then the boat will

be at the center of the newly zoomed view. If auto center is not checked, then the zooming will be centered

on the position of the cursor.

Show Scale

When depressed, a range scale showing distances in the current system units will be displayed on the left

hand side of the chart as shown in Figure 4.1, SonaSoft Chart Display. The units of this scale are

displayed in the system units selected in the Configuration Manager's System Settings tab.Note: the scale

is adjusted for the current zoom level.

Mouse Controls

Left Button Mouse Drag

Dragging the mouse with the left mouse button down will pan the chart image.

Right Button Mouse Drag

Dragging the mouse with the right mouse button down will draw an orange range line from the initial mouse

position when first depressed to the final mouse position when released. While the button is depressed,

the length of the line specified in system units will be drawn near the mouse. Once released, the distance

will be displayed along the orange line.

Configuration Manager OptionsIn order for this component to work properly, NMEA compatible heading and location sensors must be

connected to the SonaSoft User Interface computer. These sensors include: gps, loran, compass, etc.

More information on NMEA connections can be found in the chapter entitled Chapter 6, Connecting NMEA

Devices. Under the the Configuration Manager's Chart Display tab, the user can specify the type of NMEA

message to use. The user can select between RMC (recommended minimum Specific GNSS data), GGA

(Global Positioning System Fix Information), HDG (Heading, Deviation, and Variation) and HDT (Head-

ing True) where appropriate

Figure 4.2. Chart Display Configuration Manager Options


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Chart Display

21

History Length

Every time a new latitude and longitude position is received by the system, the vessel's position is updated

on the chart. A blue dot is placed on the chart at previous locations. The number of most recent locations

noted is defined by the History Length setting. A setting of 0 removes all history markings from the chart.

Show Heading

If this option is selected, the vessel's heading as received from the selected NMEA message is displayed

as text on the chart next to the vessel's icon.

Show Lat/Long of Cursor

If this option is selected, the latitude and longitude at the cursor's position is shown in the lower left hand

corner of the chart. If the cursor moves off the chart, the text no lat/long info is displayed. In Figure 4.1,

SonaSoft Chart Display, the cursor was not over the chart when the screen shot was made. Therefore,

the no info message is displayed.


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22

Chapter 5. Nav Info Display

Overview

The Nav Info Display provides basic conning information (Depth, Heading, Position, and Speed) to theuser in a text format when external NMEA sensors are connected to the SonaSoft user interface computer.

Figure 5.1. The Nav Info Display

When available, the most recently received conning information is shown in this display. If a particular

sensor is not available, that portion of the Nav Info Display will contain dashes to reflect the missing

information. If the user knows that there is no data available for a particular type of conning info, he/she

may un-check the "Listen" option in the Configuration Manager's NMEA Settings menu to supress that

type from being displayed as dashes this display. Please see the section called NMEA Message Selection

for more details.

Configuration Manager Options

In order for this component to work properly, NMEA compatible depth, heading, GPS, and speed sensors

must be connected to the SonaSoft User Interface computer. These sensors include: echo sounder, GPS,gyro-compass, Doppler speed log, paddle wheel transducer, etc. More information on NMEA connections

can be found in the chapter entitled Chapter 6, Connecting NMEA Devices. Under the the Configuration

Manager's NMEA Settings menu, the user can specify the type of NMEA message to use.

For echo sounder depth, the user can select from the following NMEA messages:

DBT: Depth below transducer.

DPT: Depth below the transducer with reference to keel or surface.


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Nav Info Display

23

For vessel heading, the user can select from the following NMEA messages:

HDG: Heading, Deviation, and Variation.

HDT: Heading True.

RMC: Recommended minimum Specific GNSS data.

VHW: Water Speed and Heading.

VTG: Course over ground and ground speed.

Due to the sensor type the data provided may be either heading or course. For example, some GPS units

may output a message that is intended as heading yet the instrument fills the particular values with course

data. You should consult your sensor's documentation to be sure of the information type displayed in

SonaSoft's Vessel Heading Display. Some messages provide heading in either sensor heading/course val-

ues, magnetic heading/course values, or true heading/course values. When available, the user can select

the values they prefer.

For vessel position, the user can select from the following NMEA messages:

GGA: Global Positioning System Fix Data.

GLL: Geographic Latitude and Longitude.


For vessel speed, the user can select from the following NMEA messages:


VHW: Water Speed and Heading.

VTG: Course over ground and ground speed.

Some messages provide speed in either knots or km/h. When available, the user can select the units they

prefer.


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24

Chapter 6. Connecting NMEA Devices

Overview

The SonaSoft user interface software has been designed to interface with external navigation sensorsvia standard NMEA 0183 interface sentences. It is highly recommended that a GPS, echo sounder, and

heading sensor (if available) be connected to the SonaSoft computer. For vessel speeds up to 10 knots,

FarSounder's 3D sonar display capability does not require any external nmea sensors.

Figure 6.1. COM Port NMEA configuration options

However, in order to take full advantage of SonaSoft's navigation display capabilities, external sensors

are needed for features such as:

plotting the ship's location on top of a digital chart

showing the Depth Profile angle in absolute heading

displaying vessel speed

displaying vessel heading

displaying vessel position


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Connecting NMEA Devices

25

displaying echo sounder information

The SonaSoft software has been designed to accept information from external sensors via standard

NMEA-0183 sentences. SonaSoft connects to these NMEA sensors via the host computer's COM ports.

SonaSoft can listen to and process the following sentences: RMC, VHW, VTG, HDG, HDT, DBT, DPT.

In most cases, the host computer's COM ports will be basic serial ports (RS-232). However, some marine

computers come equipped with true NMEA-0183 hardware ports (opto-isolated RS-422). In all cases,

these COM port settings can be configured under the Configuration Manager's COM Port NMEA tab. If

the host computer has multiple COM ports, the software can be configured to listen on multiple ports to

multiple sensors. Additionally, a standard NMEA multiplexer can be used to connect multiple sensors to

a single COM port.

COM Port Configuration

Upon viewing the Configuration Manager tab, a list of all available COM ports on which SonaSoft can

listen will be generated. Each row in the list contains a check box, a COM port number, a baud rate selection

drop down box, and a Show Trace button. SonaSoft can read all standard NMEA-0183 messages on

any COM port in the list.

COM Port Check Box

The check boxes indicate on which COM ports the SonaSoft should listen (an empty box indicates that

the port is not being used, a red check indicates that the port is in use). When the checkbox is checked,

the show trace button will be active.

Baud Rate Drop Down Box

The baud rate for each COM port is selected with this drop down selection box.

Show Trace ButtonPressing the Show Trace button will pop up a window where the user can see all of the COM port data

being read off the port.

Re-Scan for Available Ports Button

This button will re-scan to find any available COM ports for SonaSoft to listen on. Available COM

ports will be listed in the COM port list.

NMEA Message Selection

At the bottom of this window, there are four rows of dop-down selectors where the NMEA messages to

be used for Depth, Heading, Position, and Speed can be selected. The Heading and Speed selections also

have a second drop-down selector for configuring options specific to certain messages. SonaSoft will

only listen to the messages selected for each data type.

Each message type (Depth, Heading, Position, and Speed) also has a "Listen" check box option. When

"Listen" is unchecked, SonaSoft will not listen for any messages of that type. For example, if there are

no Depth messages available on any of the COM ports selected, then the "Listen" checkbox for Depth

messages can be unchecked.


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Connecting NMEA Devices

26

NOTE: Message selection is independant of COM port selection. This means that if a particular message

is selected for a given data type, it does not matter on which COM port it is received.


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27

Chapter 7. System Settings Options

Overview

There are a number of System Settings inside SonaSoft. These settings are general configuration op-tions which are used throughout the software. These settings are found under the Configuration Manager's

System Settings tab.

Figure 7.1. System Settings dialog box

System Depth Units

The units selected from this drop down box are used for depth measurements throughout various displays

and setting controls within SonaSoft. The following units are supported: feet, meters, fathoms.

System Range Units

The units selected from this drop down box are used for range measurements throughout various displays

and setting controls within SonaSoft. The following units are supported: feet, yards, meters, kilometers,

miles (statute), miles (nautical), cables.

Set Vessel Draft

The value entered here is used for all calculations within SonaSoft which require knowing the draft of

the vessel. For large vessels that frequently load and discharge cargo or fuel, this value may need to be

updated frequently. Smaller vessels may never need to update this value.Note: To ensure that all displayed

depths are correct, it is REQUIRED that this value is correctly updated.


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System Settings Options

28

Advanced Settings

The current version of SonaSoft has a single advanced setting. This setting is the transducer depth

relative to the vessel's keel or deepest draft location on the hull. This value is REQUIRED for setting all

depth information relative to the surface or the keel. Positive values indicate that the transducer is above

the keel. Negative values indicate the transducer is below the keel. This value is generally set once atinstallation, and does not need to be updated unless the installation is modified.


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29

Appendix A. UnderstandingInterference and Other Limitations

OverviewFarSounder has developed advanced signal processing algorithms that allow the software to operate largely

without significant user input. These algorithms represent the state of the art in forward looking, obstacle

avoidance sonar technology. However, like any shipboard tool, Forward Looking Sonar will not solve

every problem 100% of the time. It will, however, solve many problems most of the time. It is therefore

important to accurately understand how interference and other limitations effect the system's performance.

Other Sonar Interference

FarSounder's sonars operate at 60 kHz. The most common echo sounder frequency is 50 kHz. Since these

frequencies are close to one another, users may sometimes experience interference from other sonars.Generally, interference is only experienced when the echosounders on large commercial ships are close

to the user's vessel and when the FarSounder is pointed towards the other ship. Such interference appears

on the FarSounder display as a ring of echoes all at the same range as shown in Figure A.1, Echo

sounder interference. Usually, they appear as in-water targets, but sometimes they can also appear as a

raised mound or sharp dip in the sea bottom at all angles. The interference can also be seen in the System

Status's Hydrophone Data display as shown in Figure A.2, Echo sounder interference and Figure A.3,

Echo sounder interference. In this view, the interference appears as sharp spikes in the signal at reg-

ular intervals. Generally, between 6 and 20 spikes will be present at a time in the Hydrophone Data Dis-

play. It is important to realize that if another vessel is interfering with the FarSounder sonar, this usually

means the area is well trafficked and often well known. Locations where the FarSounder sonar is most

valuable, echosounder interference is usually not present. Generally, the FarSounder will not interfere with

echosounders.


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Understanding Interfer-

ence and Other Limitations

30

Figure A.1. Echo sounder interference

Dolphins and porpoise are another source of interference similar to echosounders. When dolphins or por-

poise are near the vessel or playing in the bow wake, interference will often be present. This is from the

animals' own sonar systems pinging back at the FarSounder sonar. Though FarSounder's sonars operate

outside the hearing ranges of the great whales, dolphins and porpoises can hear the transmissions just as

they do those of echosounders. FarSounder has taken great care in ensuring that their sonars will not cause

any harm to any marine life. The duty cycles and transmit powers are significantly lower than those of

other marine acoustic systems that are commonly accepted throughout the world. In fact, FarSounder's

products have been reviewed by scientists at the National Marine Fisheries Service and been found to have

no negative impact on the marine environment 1.


1"NOAA's Ocean Acoustics Program (NMFS Office of Science and Technology) has assessed the technical specifications of the current version of

the FarSounder sonar technology and concurs that, based on the sound source level, signal duration, directionality, and operational frequency band,

there are no anticipated injurious effects on marine mammals or other marine species from it's deployment." --Brandon Southall, NMFS


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31


Bubble Cloud/Wake Interference

Bubbles make really good sonar reflectors. This means that bubbles will interfere any sonar by creating

echo returns at the bubble's location and blocking sound from passing through a bubble cloud. This effect

is not unique to FarSounder sonars. Rather this effect is true for all sonar technologies. Bubble clouds

consisting of large bubbles tend to reflect echos back to the sonar and prevent sound energy from continuing

beyond the bubble cloud. Bubble clouds consisting of small bubbles tend to dissipate the sound energy

by dispersing the echos in many directions. They also prevent sound energy from continuing beyond the

bubble cloud, but they don't generally reflect a lot of echo back to the sonar. In both cases, the larger the

bubble cloud, the more energy from the sonar is disrupted. Bubbles are produced by a variety of things

such as waves, vessel wakes, and turbulent current flows around stationary objects like pilings and buoys.

Each of these types of bubbles clouds will effect FarSounder sonars differently.

Waves produce bubbles by forcing pockets of air down into the water column as the waves splash and

break. The bigger the waves, the more air bubbles will be pushed deeper into the water. It turns out, that

most bubbles from most waves most of the time in most waters are in the upper 6 feet of the water column.This means that the deeper the sonar is installed on the vessel, the better the system will perform in worse

sea conditions. Bubbles created by waves will often show up as in-water targets. They will be transient

(meaning they do not always show up in the same place) and will often be slightly less reflective than

large navigation obstacles. Like radar, higher sea states will cause more interference with the sensor. Like

increasing a radar's wave reject setting, increasing the sonar's In-Water Squelch setting a few decibels will

often remove much of the wave induced noise reflections. Also like radar, this will have the cost of not

detecting actual smaller objects. It is recommended that the user view the 3D Sonar Display with color

mapped to Signal Level to best determine the general reflectivity level of the wave induced bubbles. From

this, the user can set the In-Water Squelch appropriately.

Vessel Wakes are another source of bubbles. Their bubbles are created by the hull forcing air into the

water as the vessel cuts through the water and by the propulsion system creating cavitation. Vessel wakes

generally reach a depth no greater than the draft of the vessel from which they were created. These bubblesclouds tend to be a mixture of large and small bubbles. The larger bubbles reflect strong echoes back to the

sonar and dissipate relatively quickly (generally within a couple of minutes). The smaller bubbles tend to

disburse the sonar energy without reflecting many strong echoes back to the sonar. They dissipate slowly

and can be trapped in the water for 10 minutes or more. Generally, if the path of the vessel is still visible

at the surface of the water, wake induced bubbles are still present.


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32

Figure A.4. Wake interference

From far away, vessel wakes generally appear on the sonar as a long line of in-water targets similar to a jetty

or pier wall. However, once the sonar enters the wake area, normal operation will generally be disrupted

since the bubbles are blocking the outgoing transmit energy directly at the transducer. When inside a wake,

the Hydrophone Data viewer inside the System Status Display will show a short period of strong energy

followed by a period of almost no energy. Figure A.4, Wake interference shows an example of the sonar

inside a wake. The short, strong energy seen is the transmit signal as it passes through the transducer before

the bubbles block the signal. Once the sonar passes through a wake, normal operation will resume.

Turbulent Current Flows around stationary objects like pilings and buoys produce bubble clouds mostly

through cavitation. In general, these bubble clouds consist of small to medium sized bubbles. This means

that sometimes the object in the water creating the turbulence will be masked by the small bubbles dis-

sipating the sound with few strong reflections back to the sonar. Generally, this effect will only be seen

when approaching such objects from down current. In other situations, the mediums sized bubbles will

dominate and the sonar will detect a slightly fluctuating tail to the actual object. Like wakes, if the sonar

enters a turbulence field, normal operation of the sonar will generally be disrupted until the sonar passes

through the turbulence.

Sea State Limitations

In addition to creating bubbles, increased sea states can have additional effects on the sonar system. The

most obvious is transducer movement. Inside the Transducer Module is a roll and pitch sensor. This sensor

will significantly stabilize the image shown to the user when the vessel is undergoing rolling and pitching

up to 20 degrees. Though the Transducer Module should stay submerged, should heavy pitching bring the

unit out of the water occasionally, the unit will not be damaged. However, should the unit be transmitting

or receiving during that period, no image will be seen. Additionally, if the unit is in the water and a wave

trough is between the sonar and a target of interest, the trough will block the sonar from seeing the target.

The sonar works as a line of sight system and sonar energy cannot cross the water/air boundary.

Vessel Speed LimitationsFarSounder's FS3 and FS3-DT sonars are designed for up to 20 knots operational vessel speed. This rating

is based upon an ideal installation. Some vessels have significant mechanical vibration or create turbulence

in front of the Transducer Module. In these cases, system performance may degrade a speeds less than 20

knots. Going beyond 20 knots will not damage the system. However, at higher speeds, performance will

decrease as speed increases. That being said, some FarSounder customers have reported good performance

even at speeds over 25 knots.


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Appendix B. Understanding WaterDepth Performance

Besides operating as a true 3D sonar, creating a 3D image with a single ping, FarSounder's technology

distinguishes itself as a shallow water sonar system with its impressive Water Depth Performance and

its ability to detect objects in shallow water even beyond its water depth limit. To best understand how

FarSounder's technology is able to operate so well in shallow water it is first necessary to understand the

metrics used in shallow water sonars.

There are two metrics used when talking about the maximum range of a forward looking sonar: Maximum

Range and Water Depth Performance. Both of these metrics are important, yet most other Forward Looking

Sonar products do not like to talk about their Water Depth Performance.

Maximum Range is the farthest distance at which the system can detect targets under ideal conditions. This

range is absolute and varies based on a target's acoustic reflectivity. Generally, larger objects have more

reflectivity. However some materials and shapes also effect a target's acoustic reflectivity. In some cases,

a large object who's material or shape does not reflect well will not be detected as well as smaller

objects who's material and shape do reflect well. Good reflecting targets will be detected at the full range

of the sonar. Weaker reflectors will be detected at shorter ranges.

Water Depth Performance is the ratio between the depth of water below the transducer and the range at

which the sea bottom can be mapped. As an example, if a 2 water depth sonar system is operating in 50

feet of water, that system can generate bottom maps only out to 100 feet. Water Depth Performance is

limited by various physical effects. When a sound wave is transmitted from the sonar and reflects off the

sea bottom, some of the energy reflects back to the sonar and some of the energy reflects forward. The

percentage of energy reflected back to the sonar's receiver is a function of the sea bottom's material type and

shape as well as the angle at which the sound wave hits the sea bottom. Hard rough sea bottom materials

like rocks and sand reflect better than soft materials like mud and silt. Likewise, steeper angles reflect

more energy back to the sonar than shallow angles. Therefore, as range increases, the angle at which the

incoming sound wave hits the sea floor becomes shallower. At some angle, not enough energy is reflected

back to the receiver to allow for sea bottom detection and mapping.

One of the most impressive features of FarSounder's technology is its shallow water capability. Though

FarSounder's products are specified as 8 Water Depth systems, 10+ Water Depth performance can some-

times be achieved in certain conditions. However, even beyond their water depth capability, FarSounder

sonars are still able to detect objects out to farther ranges. For instance, in shallow water areas, FarSounder

systems can not only create bottom maps to 8 water depths but also detect in-water targets and targets

sticking up off the sea floor up to the full range of the sonar over the entire field-of-view. In these cas-

es, the sonar may not be able to determine the actual depth of the long range, in-water target, but it is

able to tell the user that something is there. Please visit the screen shots gallery at www.farsounder.com

[http://www.farsounder.com] for examples of shallow water operation at ranges well beyond our water

depth capability.
http://www.farsounder.com/http://www.farsounder.com/http://www.farsounder.com/http://www.farsounder.com/

son as oft manual

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